This invention relates to communications over a power distribution network to, for example, supply electricity from a utility to consumers. More particularly, the invention is directed to the simultaneous detection of communications signals, specifically those sent from consumer facilities back to the utility, on all phases of the utility's power distribution network.
Communications systems employed by electrical utilities are known in the art. See for example, U.S. Pat. Nos. 6,940,396 and 5,262,755. Typically, the utility uses the system to send messages or commands (outbound signals) from a transmitter location (usually at a network substation) to consumer facilities. A transceiver which is typically incorporated in meters at the respective facilities, in response to the execution of a command or a request for information, then sends a signal (an inbound signal) back to the utility.
Previously, equipment located at the utility for receiving incoming messages did not have the capability to simultaneously receive messages on multiple phases of the network. Now, however, the receivers do have this capability; and, since there is usually a part of the inbound signal present on all three phases of the network, combining the signals on all the phases can yield optimal signal strength.
One communications system used by utilities is a two-way automatic communications systems, or TWACS®. In earlier implementations of this system, inbound signal detection hardware only had the capability to sample a signal on one phase at a time. Current signal detection hardware now has the capability to sample signals on all inputs (phases) to a substation simultaneously. A method for detection of signals transmitted simultaneously on multiple phases is disclosed in U.S. Pat. No. 6,940,396, but that method is designed for detecting signals on one phase at a time and relies on temporal differences between signals to separate them. Depending upon the wiring configuration, all inbound signals appear on at least two of the three phases (or four phases if a neutral phase is present) available at the substation, and optimal detection of inbound signals should therefore include signals from these multiple phases. Heretofore, however, that has not been possible. Using the method of the invention for performing “all-phase” detection, and which operates in a concurrent phase mode, it now is.
In addition to all-phase detection producing a higher signal strength signal, optimizing the signal-to-noise ratio (SNR) of a combined signal also requires that the detection method take into account correlation, if present, in the noise signals on the various phases. In accordance with the method of the invention, the signal strength and noise correlations are estimated adaptively for each inbound signal and the resulting combining scheme should produce higher signal-to-noise ratios.
Finally, previous implementations of concurrent-phase methods were complex, requiring separate signal-processing algorithms for detection and for canceling interference from signals on other phases. The method of the present invention integrates these algorithms, with the resulting single algorithm simultaneously producing better communication performance and reduced computational requirements relative to previous algorithms.